Abstract: A transmitter device comprises a first predistortion circuit and a second predistortion circuit having at least one correction stage provided with a correction path for determining a correction term. The correction term for each source signal is a function of a corresponding symbol of a predefined constellation for each source signal and of the output of a model having a circuit to emulate modulation means and the second predistortion circuit, a circuit to emulate a non-linear transmission link over which a predistorted version of an aggregate pulse-shaped signal is to be transmitted for amplitude levels before saturation of an AM/AM characteristic of the transmission link occurs and to emulate the non-linear transmission link for amplitude levels beyond saturation of the AM/AM characteristic, and a circuit to emulate demodulation means.

Abstract: A receiver device for a communication system is arranged for receiving a signal comprising a plurality of transponder signals each containing a plurality of carrier signals and comprises: an adjustable spectral filter configurable for selecting a desired transponder signal. Means for performing a non-linear transformation on the selected desired transponder signal, whereby the non-linear transformation is represented by a set of parameter values. At least one receive filter configurable to select at least one desired carrier signal of the non-linearly transformed selected desired transponder signal and, performance measuring means for determining one or more performance metrics on at least one carrier signal of the plurality of carrier signals contained in the desired transponder signal to obtain the set of parameter values.

Abstract: The present invention is related to a device for generating waveguide modes for use in a feed horn of a satellite antenna system, said waveguide modes comprising at least one excitation mode of higher order than the fundamental mode, said device comprising a waveguide containing a first waveguide section with at least three longitudinal slots extending in the inner side of said waveguide, characterized in that said waveguide contains a second waveguide section with at least three longitudinal slots extending in said inner side of said waveguide.

Abstract: A method of digital modulation comprises generating a stream of modulation symbols in order to produce a modulated signal. The modulation symbols belong to a multi-ring digital signal constellation having all signal points placed on at least two concentric rings. The total number of signal points is larger than 8, and at least one ring has unequally spaced points constructed to form together with at least one neighbouring ring a subset of neighbouring rings. Each signal point of the subset has a unique angular coordinate modulo 2? and the angular spacing of the signal points of the subset is uniform.

Abstract: A predistortion circuit for countering interference affecting a digital signal during transmission over a transmission link comprises a path of the digital signal between a mapper at a transmitter side and a demapper at a receiver side. The predistortion circuit is arranged for receiving a version of a digital symbol selected from a predefined constellation used for mapping a bit stream, and includes at least one correction stage provided with a correction path arranged for determining a correction term as a function of the output of a model equivalent to the transmission link and a corresponding symbol of a target constellation. The position of the target constellation points is determined using a measure accounting for the transmission link. The predistortion circuit is arranged for adding the correction term to the received version of the digital symbol and outputting the result of adding as an updated version of the digital symbol.

Abstract: A device for predistortion and pulse shaping filtering in a communication system includes input scaling means arranged for scaling an applied transmit symbol with an adaptable input gain scaling factor, and a pulse shaping filter and a predistortion unit arranged for applying on the input gain scaled transmit symbol in either order a filtering operation and a non-linear predistortion operation to obtain a predistorted signal. The non-linear predistortion operation is represented by a set of parameter values selectable among a plurality of given sets of parameter values. The predistortion unit is arranged for selecting the set of parameter values exploiting a given performance measure. The device includes output scaling means arranged for scaling the predistorted signal with an output gain scaling factor to obtain a transmit signal. The adaptable input gain scaling factor and the output gain scaling factor are precalculated values corresponding to the selected set of parameter values.

Abstract: A predistortion circuit for countering interference affecting a digital signal during transmission over a transmission link comprises a path of the digital signal between a mapper at a transmitter side and a demapper at a receiver side. The predistortion circuit is arranged for receiving a version of a digital symbol selected from a predefined constellation used for mapping a bit stream, and includes at least one correction stage provided with a correction path arranged for determining a correction term as a function of the output of a model equivalent to the transmission link and a corresponding symbol of a target constellation. The position of the target constellation points is determined using a measure accounting for the transmission link. The predistortion circuit is arranged for adding the correction term to the received version of the digital symbol and outputting the result of adding as an updated version of the digital symbol.

Abstract: An FDM-CPM multi-user detector (30) jointly detects the received symbols for all users by determining from the received multi-user signal an a-posteriori probability mass function (pmf) of a time-sequence of states and transmitted symbols of all users, by iterative message passing corresponding to a specific factorisation of the pmf. The factorisation involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative process convergent. Non exponential complexity is enabled by disregarding multiple access interference (MAI) from at least some of the other users. Applications can include hubs for satellite communication ground stations.

Abstract: A multi-band transducer is described incorporating a coaxial waveguide interface for use with a multi-band feed and incorporating bent shaped probes yielding all-planar interfaces in microstrip for all frequency ranges and suitable for mass production. Hybrids can be incorporated for linear or circular polarization applications.

Abstract: Methods and apparatus are described for management of traffic comprising a statistical shaper having a plurality of inputs each for receiving a data stream and a plurality of outputs forming a variable rate bit streams; a multiplexer which combines the bit streams to form an output stream; a modulation stage which is operable to use one or more of a plurality of different modulation schemes to modulate the bit streams onto an output bearer; and, a controller which is operable to control the amount of data arriving at the modulation stage. The controller performs rate control of the data arriving at the modulation stage so that the rate of data output in the output stream from the modulator stage is within a predetermined limit for the transmission channel. For example if the modulation rate for any one bitstream changes, this would alter the rate of data transmission after the modulation stage except that excess data is stored in buffers.

Abstract: A multi-band transducer is described incorporating a coaxial waveguide interface for use with a multi-band feed and incorporating bent shaped probes yielding all-planar interfaces in microstrip for all frequency ranges and suitable for mass production. Hybrids can be incorporated for linear or circular polarization applications.

Abstract: A dual band, higher and lower frequency range transducer with a circular coaxial waveguide feed is described having a first junction for connection of a lower frequency range outer waveguide of the coaxial waveguide feed to at least two rectangular or ridge waveguides offset from the longitudinal axis of the transducer and a second junction for connection of the at least two rectangular or ridge waveguides to a further waveguide. A third junction is provided for connecting an inner waveguide of the coaxial waveguide feed to a higher frequency range waveguide. The transducer comprises at least first and second parts joined across a first plane substantially perpendicular to the longitudinal axis and including at least a portion of the higher frequency range waveguide extending within the first plane of the join. A seal such as an “O” ring seal may be placed easily in the plane of the join thus preventing moisture ingress.